Stihl MS261 Keeps throwing the chain off

[forstmeister]

Hey everyone, I bought a Stihl MS261 last fall to replace my Husky 345XP that finally died...but the title says it all. Within 1-2 hours it threw the chain and wrecked it. The tip of the bar got tweaked as well so I had to replace everything. Well a few more hours in and it threw the chain again. It's got an 18" bar with pro chains so far...but I am really confused why this keeps happening.

I run a MS201TC for tree work, and have a MS362 as well as a 660 so I am pretty well versed with Stihl saws.

Anybody else run into this with a newer Stihl?

 

[EchoShindaiwaMakitaDolmar]

Are you making any chain adjustments within that first few hrs- perhaps you're having excessive chain stretch?

 

[farmer steve]

No issues with mine. What size chain and we're sure it matches the sprocket? Hard to be an internet mechanic without asking questions.

 

[forstmeister]

No issues with mine. What size chain and we're sure it matches the sprocket? Hard to be an internet mechanic without asking questions.

Running a .325 chain on an 18” bar, straight from the dealer. Drive gauge matches

 

[forstmeister]

Are you making any chain adjustments within that first few hrs- perhaps you're having excessive chain stretch?

I’ve never made a habit of adjusting my chain that frequently. I’m not loving these chains though for other reasons, but I didn’t want the low kickback chains either.

 

[GrizG]

What are you cutting? The only time I've had a problem like this is when cutting vines and saplings that grab the chain by pinching it... or by not watching the chain tension on new chains.

 

[Mad Professor]

Running a .325 chain on an 18” bar, straight from the dealer. Drive gauge matches

Did you check the chain/bar/sprockets?

Is this new or used?

I've never ruined a sprocket tip from throwing a chain.

Post some pictures of present and past setups.

 

[TheJollyLogger]

I’ve never made a habit of adjusting my chain that frequently. I’m not loving these chains though for other reasons, but I didn’t want the low kickback chains either.

What do you mean you'vnever made a habit of adjusting your chain that frequently? How often do you check the tension?

 

[stihltech]

You say gauge matches. With 63 and 50 gauge now in the mix, please be sure.

 

[cookies]

Check the bar's tip, the roller sprocket's bearings may be bad. Had this happen to me 2 weeks ago with a practically new 18" .325 .063 stihl laminate bar I made a couple bore cuts with.

 

[forstmeister]

Did you check the chain/bar/sprockets?

Is this new or used?

I've never ruined a sprocket tip from throwing a chain.

Post some pictures of present and past setups.

The sprocket wasn’t damage. When the chain came off the drive channel got tweaked and developed a bump that prevents the sprocket from turning smoothly.

 

[fields_mj]

The sprocket wasn’t damage. When the chain came off the drive channel got tweaked and developed a bump that prevents the sprocket from turning smoothly.

That would be a good reason why you keep throwing it. If there's anything wrong out at the nose of the bar, that will be the most likely cause of your repetitive issue. Having said that, like the others, I've never had an instance where throwing a chain damaged anything on the bar so I'm not sure how that would happen. If the bump can be filed down, that would help. I want to say to try flipping the bar, but that's not going to fix any damage.

As far as tension goes, on a new chain, I start off running them on the tight side because they tend to loosen up pretty quick as they break in. When new, I check my tension after every tank or two, and frequently have to tighten it. After a few tanks, things settle in and they rarely need adjusted.

 

[forstmeister]

I replaced the damaged bar. the new bar/chain combo also threw the chain.

Guess I’ll just need to check these chains more frequently than I’ve done in the past.

 

[TheJollyLogger]

I replaced the damaged bar. the new bar/chain combo also threw the chain.

Guess I’ll just need to check these chains more frequently than I’ve done in the past.

Yes, check it constantly, especially a new chain

 

[muddy42]

Was the sprocket worn, these need to be replaced approximately at the same interval as the bar?
Did the chain appear to fit the sprocket and ride over bar tip correctly by hand? When I've tried to fit the wrong combination of bar, chain or sprocket it is pretty obvious if something is wrong.
If everything matches, you really shouldn't be throwing chains, whatever the chain tension.

 

[pdqdl]

As far as tension goes, on a new chain, I start off running them on the tight side because they tend to loosen up pretty quick as they break in

While it is true that chains seem to "stretch" faster when they are new, making them tight is only going to accelerate the wear.

Running any chain too tight will accelerate wear on the bar, sprockets, and the chain. I don't think you are helping yourself with that practice.

---

Regarding throwing the chain: I've always found that if a chain won't stay on, it is mostly an operator problem, and after that, you should consider bar & chain mismatch, how it is assembled, and how much wear is involved. I'm not going to point any fingers, but if you are an experienced user on a new bar & chain, how it is assembled seems like the most likely source of the problem.

I'd put it all together, tighten the bar & chain, then turn it upside down and confirm that the chain is running true & perpendicular into the clutch & drive sprocket. Running a bar crooked to the crankshaft is a reliable way to throw a chain. Maybe someone grabbed your saw when you weren't looking, and bent the bar. Look down it carefully for anything that isn't straight.

On the other end of that chain; dismounting a chain at the tip of the bar seems unlikely unless you are clumsy with the saw when it has a loose chain. Hitting brush and twigs will do it, but it seems unlikely to be worse on your new Stihl than any other saw you have used in the past.

 

[stobrien69]

Hey everyone, I bought a Stihl MS261 last fall to replace my Husky 345XP that finally died...but the title says it all. Within 1-2 hours it threw the chain and wrecked it. The tip of the bar got tweaked as well so I had to replace everything. Well a few more hours in and it threw the chain again. It's got an 18" bar with pro chains so far...but I am really confused why this keeps happening.

I run a MS201TC for tree work, and have a MS362 as well as a 660 so I am pretty well versed with Stihl saws.

Anybody else run into this with a newer Stihl?

Hard to really know without seeing it but to me it sounds like the chain was stretched at some point. Unless one of the teeth bent when it came off the first time. If neither one of those are the issue then check your adjuster to make sure there's no play in it.

 

[blades]

Hard to get those easy single tighten bars tight to hold tension - been discussed in other forms. if that is what you have. Don't know what it is but this last year I have been having trouble with various brands of 3/8 .050 chain- stretching quite a bit. one bucking cut 20" ash and I have tighten it up again multiple bars and saws. .063 holding ok, will have try some .058 in 3/8 - more bars $. 325 on corded electric is a little finicky also ) Makita saw.

 

[lloyd786]

Hey everyone, I bought a Stihl MS261 last fall to replace my Husky 345XP that finally died...but the title says it all. Within 1-2 hours it threw the chain and wrecked it. The tip of the bar got tweaked as well so I had to replace everything. Well a few more hours in and it threw the chain again. It's got an 18" bar with pro chains so far...but I am really confused why this keeps happening.

I run a MS201TC for tree work, and have a MS362 as well as a 660 so I am pretty well versed with Stihl saws.

Anybody else run into this with a newer Stihl?

Grooved up sprocket? My friend ,fellow landscaper, brought me his saw that was doing the same. Turns out he put his cover on with the chainbrake set and when it tried to jump on the clutch it threw the chain. Could be a wore out clutch bearing too.